The Role of iPSC Modeling Toward Projection of Autophagy Pathway in Disease Pathogenesis: Leader or Follower. Stem Cell Rev Rep. 2021;17:539-561. [PMID: 33245492 DOI: 10.1007/s12015-020-10077-8]

Activation of AMPK promotes cardiac differentiation by stimulating the autophagy pathway

Autophagy, a critical catabolic process for cell survival against different types of stress, has a role in the differentiation of various cells, such as cardiomyocytes. Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) is an energy-sensing protein kinase involved in the regulation of autophagy. In addition to its direct role in regulating autophagy, AMPK can also influence other cellular processes by regulating mitochondrial function, posttranslational acetylation, cardiomyocyte metabolism, mitochondrial autophagy, endoplasmic reticulum stress, and apoptosis. As AMPK is involved in the control of various cellular processes, it can influence the health and survival of cardiomyocytes. This study investigated the effects of an AMPK inducer (Metformin) and an autophagy inhibitor (Hydroxychloroquine) on the differentiation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). The results showed that autophagy was upregulated during cardiac differentiation. Furthermore, AMPK activation increased the expression of CM-specific markers in hPSC-CMs. Additionally, autophagy inhibition impaired cardiomyocyte differentiation by targeting autophagosome-lysosome fusion. These results indicate the significance of autophagy in cardiomyocyte differentiation. In conclusion, AMPK might be a promising target for the regulation of cardiomyocyte generation by in vitro differentiation of pluripotent stem cells.

Revisiting the Role of Autophagy in Cardiac Differentiation: A Comprehensive Review of Interplay with Other Signaling Pathways

Autophagy is a critical biological process in which cytoplasmic components are sequestered in autophagosomes and degraded in lysosomes. This highly conserved pathway controls intracellular recycling and is required for cellular homeostasis, as well as the correct functioning of a variety of cellular differentiation programs, including cardiomyocyte differentiation. By decreasing oxidative stress and promoting energy balance, autophagy is triggered during differentiation to carry out essential cellular remodeling, such as protein turnover and lysosomal degradation of organelles. When it comes to controlling cardiac differentiation, the crosstalk between autophagy and other signaling networks such as fibroblast growth factor (FGF), Wnt, Notch, and bone morphogenetic proteins (BMPs) is essential, yet the interaction between autophagy and epigenetic controls remains poorly understood. Numerous studies have shown that modulating autophagy and precisely regulating it can improve cardiac differentiation, which can serve as a viable strategy for generating mature cardiac cells. These findings suggest that autophagy should be studied further during cardiac differentiation. The purpose of this review article is not only to discuss the relationship between autophagy and other signaling pathways that are active during the differentiation of cardiomyocytes but also to highlight the importance of manipulating autophagy to produce fully mature cardiomyocytes, which is a tough challenge.

Fountain of youth—Targeting autophagy in aging

As our society ages inexorably, geroscience and research focusing on healthy aging is becoming increasingly urgent. Macroautophagy (referred to as autophagy), a highly conserved process of cellular clearance and rejuvenation has attracted much attention due to its universal role in organismal life and death. Growing evidence points to autophagy process as being one of the key players in the determination of lifespan and health. Autophagy inducing interventions show significant improvement in organismal lifespan demonstrated in several experimental models. In line with this, preclinical models of age-related neurodegenerative diseases demonstrate pathology modulating effect of autophagy induction, implicating its potential to treat such disorders. In humans this specific process seems to be more complex. Recent clinical trials of drugs targeting autophagy point out some beneficial effects for clinical use, although with limited effectiveness, while others fail to show any significant improvement. We propose that using more human-relevant preclinical models for testing drug efficacy would significantly improve clinical trial outcomes. Lastly, the review discusses the available cellular reprogramming techniques used to model neuronal autophagy and neurodegeneration while exploring the existing evidence of autophagy’s role in aging and pathogenesis in human-derived in vitro models such as embryonic stem cells (ESCs), induced pluripotent stem cell derived neurons (iPSC-neurons) or induced neurons (iNs).

Programmed cell death in stem cell-based therapy: Mechanisms and clinical applications

Stem cell-based therapy raises hopes for a better approach to promoting tissue repair and functional recovery. However, transplanted stem cells show a high death percentage, creating challenges to successful transplantation and prognosis. Thus, it is necessary to investigate the mechanisms underlying stem cell death, such as apoptotic cascade activation, excessive autophagy, inflammatory response, reactive oxygen species, excitotoxicity, and ischemia/hypoxia. Targeting the molecular pathways involved may be an efficient strategy to enhance stem cell viability and maximize transplantation success. Notably, a more complex network of cell death receives more attention than one crucial pathway in determining stem cell fate, highlighting the challenges in exploring mechanisms and therapeutic targets. In this review, we focus on programmed cell death in transplanted stem cells. We also discuss some promising strategies and challenges in promoting survival for further study.